- In a large saucepan, melt the butter over low heat. Once melted, add the mini marshmallows and stir continuously until completely melted and smooth. 
- Remove the saucepan from heat and stir in the salted caramel sauce and vanilla extract until well combined. 
- Gradually add the Rice Krispies cereal to the marshmallow mixture, stirring until all the cereal is evenly coated. 
- Lightly grease a 9x13-inch baking dish with cooking spray or butter. Pour the mixture into the dish and press it down firmly with a spatula or your hands to create an even layer. 
- Sprinkle the sea salt over the top of the pressed mixture. Allow the treats to cool at room temperature for about 30 minutes. 
- Once cooled, cut into squares or rectangles and drizzle with extra salted caramel sauce if desired.